Gate valve

[Lan123]

Anyone in this forum has experience dealing with pump controlled knife gate valves (Resilient wedge). Application is sewage and the valve size is 42"

 

[ccfowler]

Gate valve are NOT a good choice for throttling. Expect early failures due to erosion and erratic operation due to the effects of debris in the flow. Butterfly or ball valves are better choices.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[vpl]

I agree with ccfowler that gate valves aren't a good fit for a throttling application. However, if you're looking for an isolation valve, then the knife edge valves work "ok". They might not fully seat if they sit in the open position for long periods of time.

My vote would be for a butterfly valve if you need to throttle the flow. They tend to also be a reasonable isolation valve for the size pipe you're talking about.

I consider ball valves to be best at flow isolation rather than throttling and I feel that ball valves tend to clog faster than the gate valves. Not to mention that I haven't come across a 42" ball valve.




Patricia Lougheed

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[Lan123]

VPl& CCfolwer thanks for the comments. I was thinking of a resilient wedge knife GV. I have to replace an existing large pump. The dry well is very old and small. I would have preferred to use a plug valve and a check valve on the pump discharge, or, atleast a regular resilent type gate valve and check valve. Unfortunately there is no room for these. So my last hope is a resilient wedge knife gate valve (KGV), and to prevent backflow, a pump controlled actuator for the KGV if this option is available. Do you two think that the last choice is possible? This is a sewage application. So ball or BFV is not possible.

 

[ccfowler]

I would rather use a pinch valve for this duty. They are available for larger diameters than you cite. They can be used for both control and shut-off duties.

A gate valve used for throttling is likely to just cause endless troubles. Gate valves are good for shut-off duty but not flow control.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[TenPenny]

If I understand you correctly, you don't want to throttle with the knife gate, you simply want it to be actuated by a signal from the pump, so that when the pump shuts down, the valve closes.

 

[stanier]

For sewage I would use an eccentric plug valve or pinch valve because of the stringy nature of the solids. Why do you want to throttle the pump in any event? Sewage pumps are normally stop start. They are fitted with VSDs or soft starters if line voltage is a concern on start up.

Yu havent mentioned if this is a pump station or in a sewage treatment facility where the fluid may be a specific type of treated sewage ie WAS, RAS etc.

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